Field of the Invention
An embodiment of the present invention relates generally to a mask for deposition and a method for aligning the same, and more particularly, to a mask for deposition and a method for aligning the same capable of precisely aligning a mask for deposition and a substrate.
Description of the Related Art
An organic light emitting diode (OLED) display device, which includes a hole injection electrode, an electron injection electrode, and an organic emission layer disposed therebetween, is a self-emitting type display device emitting light while annihilating holes injected from an anode and electrons injected from a cathode due to the recombination of the holes and electrons in the organic emission layer. In addition, the organic light emitting diode (OLED) display device exhibits high-quality characteristics such as lower power consumption, higher luminance, a wider viewing angle, and a higher reaction speed and therefore, has been focused as a next generation display device of a portable electronic device.
The organic light emitting diode (OLED) display device includes an organic light emitting display panel including a display substrate on which a thin film transistor and an organic light emitting element (OLED) are formed. The organic light emitting element includes an anode, a cathode, and an organic emission layer and emits light by forming excitons by holes and electrons injected from each of the anode and the cathode and shifting the excitons to a ground state.
In a flat panel display device such as the organic light emitting diode (OLED) display device, a vacuum deposition method for depositing corresponding materials such as an organic material or metals used as an electrode under the vacuum atmosphere to form a thin film on a flat panel, has been used. The vacuum deposition method is performed by disposing a substrate on which an organic thin film is grown in an interior of a vacuum chamber and by evaporating or sublimating the organic materials using a deposition source unit so as to be deposited on the substrate.
The deposition process is performed by aligning and attaching a mask for deposition including an open region, which is formed to correspond to a predetermined pattern to be formed on the substrate, on the substrate and performing a control so as to deposit a material for forming an evaporated pattern on the substrate through the open region. In the deposition process, it is important to correctly align and attach the mask for deposition on the substrate without errors.
When the substrate is a transparent substrate, however, a contrast difference between alignment marks, in particular, an angle alignment mark and a substrate (and a mask) is small due to the reflected light from the mask surface at the time of performing the measurement by the measuring device and therefore, it is difficult to confirm a location of the angle alignment mark.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the described technology and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.